Modifying The Default Vlan - 3Com 4007 Implementation Manual

Modifying the Default VLAN

The default VLAN is always associated with a VID of 1, the unspecified
protocol type (for Multilayer Switching Modules), and the name
Initially, the default VLAN is also associated with all ports and no tagging.
If necessary, you can modify the default VLAN on the modules in the
system. For example, you may want to remove certain ports. Such a
change does not prevent the system from adding a new module's bridge
ports to the default VLAN.
The default VLAN is characterized by a VID of 1 and the unspecified
protocol type. The following rules apply to the insertion of a new module:
If you have modified the default VLAN to remove all ports, the ports of
a newly inserted module are added to the default VLAN.
If you have modified the default VLAN to tag a port, the ports of a
newly inserted module are added to the default VLAN.
If you have removed and subsequently redefine the default VLAN, the
ports of a newly inserted module are added to the default VLAN.
If you have removed the default VLAN and at least one other VLAN
exists, the ports of a newly inserted module are not added to any
VLAN.
If you have removed the default VLAN and no other VLANs exist, a
new default VLAN is created containing all ports when a new module
is inserted.
To ensure that data can be forwarded, verify that a bridge port is
associated with a VLAN. This association is mandatory in allClosed mode.
If you remove the default VLAN (and you do not have other VLANs
defined for the modules in the system), your ports may not forward data
until you create a VLAN for them.
The default VLAN is the flood domain in any of the following situations:
A module receives data for a protocol that is not supported by any
VLAN on the module
A module receives data for a protocol that is supported by defined
VLANs, but these VLANs do not contain the port receiving the data.
A module receives untagged data for a port and protocol that is
supported by the switching module, but the port is tagged.
See "Rules of VLAN Operation" later in this chapter.
Port-based VLANs 267
Default
.